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#! /usr/bin/env python
#
# (C) 2001-2015 Chris Liechti <cliechti@gmx.net>
#
# SPDX-License-Identifier: BSD-3-Clause
"""\
Multi-port serial<->TCP/IP forwarder.
- RFC 2217
- check existence of serial port periodically
- start/stop forwarders
- each forwarder creates a server socket and opens the serial port
- serial ports are opened only once. network connect/disconnect
does not influence serial port
- only one client per connection
"""
import os
import select
import socket
import sys
import time
import traceback
import serial
import serial.rfc2217
import serial.tools.list_ports
import dbus
# Try to import the avahi service definitions properly. If the avahi module is
# not available, fall back to a hard-coded solution that hopefully still works.
try:
import avahi
except ImportError:
class avahi:
DBUS_NAME = "org.freedesktop.Avahi"
DBUS_PATH_SERVER = "/"
DBUS_INTERFACE_SERVER = "org.freedesktop.Avahi.Server"
DBUS_INTERFACE_ENTRY_GROUP = DBUS_NAME + ".EntryGroup"
IF_UNSPEC = -1
PROTO_UNSPEC, PROTO_INET, PROTO_INET6 = -1, 0, 1
class ZeroconfService:
"""\
A simple class to publish a network service with zeroconf using avahi.
"""
def __init__(self, name, port, stype="_http._tcp",
domain="", host="", text=""):
self.name = name
self.stype = stype
self.domain = domain
self.host = host
self.port = port
self.text = text
self.group = None
def publish(self):
bus = dbus.SystemBus()
server = dbus.Interface(
bus.get_object(
avahi.DBUS_NAME,
avahi.DBUS_PATH_SERVER
),
avahi.DBUS_INTERFACE_SERVER
)
g = dbus.Interface(
bus.get_object(
avahi.DBUS_NAME,
server.EntryGroupNew()
),
avahi.DBUS_INTERFACE_ENTRY_GROUP
)
g.AddService(avahi.IF_UNSPEC, avahi.PROTO_UNSPEC, dbus.UInt32(0),
self.name, self.stype, self.domain, self.host,
dbus.UInt16(self.port), self.text)
g.Commit()
self.group = g
def unpublish(self):
if self.group is not None:
self.group.Reset()
self.group = None
def __str__(self):
return "{!r} @ {}:{} ({})".format(self.name, self.host, self.port, self.stype)
class Forwarder(ZeroconfService):
"""\
Single port serial<->TCP/IP forarder that depends on an external select
loop.
- Buffers for serial -> network and network -> serial
- RFC 2217 state
- Zeroconf publish/unpublish on open/close.
"""
def __init__(self, device, name, network_port, on_close=None, log=None):
ZeroconfService.__init__(self, name, network_port, stype='_serial_port._tcp')
self.alive = False
self.network_port = network_port
self.on_close = on_close
self.log = log
self.device = device
self.serial = serial.Serial()
self.serial.port = device
self.serial.baudrate = 115200
self.serial.timeout = 0
self.socket = None
self.server_socket = None
self.rfc2217 = None # instantiate later, when connecting
def __del__(self):
try:
if self.alive:
self.close()
except:
pass # XXX errors on shutdown
def open(self):
"""open serial port, start network server and publish service"""
self.buffer_net2ser = bytearray()
self.buffer_ser2net = bytearray()
# open serial port
try:
self.serial.rts = False
self.serial.open()
except Exception as msg:
self.handle_serial_error(msg)
self.serial_settings_backup = self.serial.get_settings()
# start the socket server
# XXX add IPv6 support: use getaddrinfo for socket options, bind to multiple sockets?
# info_list = socket.getaddrinfo(None, port, 0, socket.SOCK_STREAM, 0, socket.AI_PASSIVE)
self.server_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
self.server_socket.setsockopt(
socket.SOL_SOCKET,
socket.SO_REUSEADDR,
self.server_socket.getsockopt(
socket.SOL_SOCKET,
socket.SO_REUSEADDR
) | 1
)
self.server_socket.setblocking(0)
try:
self.server_socket.bind(('', self.network_port))
self.server_socket.listen(1)
except socket.error as msg:
self.handle_server_error()
#~ raise
if self.log is not None:
self.log.info("{}: Waiting for connection on {}...".format(self.device, self.network_port))
# zeroconfig
self.publish()
# now we are ready
self.alive = True
def close(self):
"""Close all resources and unpublish service"""
if self.log is not None:
self.log.info("{}: closing...".format(self.device))
self.alive = False
self.unpublish()
if self.server_socket:
self.server_socket.close()
if self.socket:
self.handle_disconnect()
self.serial.close()
if self.on_close is not None:
# ensure it is only called once
callback = self.on_close
self.on_close = None
callback(self)
def write(self, data):
"""the write method is used by serial.rfc2217.PortManager. it has to
write to the network."""
self.buffer_ser2net += data
def update_select_maps(self, read_map, write_map, error_map):
"""Update dictionaries for select call. insert fd->callback mapping"""
if self.alive:
# always handle serial port reads
read_map[self.serial] = self.handle_serial_read
error_map[self.serial] = self.handle_serial_error
# handle serial port writes if buffer is not empty
if self.buffer_net2ser:
write_map[self.serial] = self.handle_serial_write
# handle network
if self.socket is not None:
# handle socket if connected
# only read from network if the internal buffer is not
# already filled. the TCP flow control will hold back data
if len(self.buffer_net2ser) < 2048:
read_map[self.socket] = self.handle_socket_read
# only check for write readiness when there is data
if self.buffer_ser2net:
write_map[self.socket] = self.handle_socket_write
error_map[self.socket] = self.handle_socket_error
else:
# no connection, ensure clear buffer
self.buffer_ser2net = bytearray()
# check the server socket
read_map[self.server_socket] = self.handle_connect
error_map[self.server_socket] = self.handle_server_error
def handle_serial_read(self):
"""Reading from serial port"""
try:
data = os.read(self.serial.fileno(), 1024)
if data:
# store data in buffer if there is a client connected
if self.socket is not None:
# escape outgoing data when needed (Telnet IAC (0xff) character)
if self.rfc2217:
data = serial.to_bytes(self.rfc2217.escape(data))
self.buffer_ser2net.extend(data)
else:
self.handle_serial_error()
except Exception as msg:
self.handle_serial_error(msg)
def handle_serial_write(self):
"""Writing to serial port"""
try:
# write a chunk
n = os.write(self.serial.fileno(), bytes(self.buffer_net2ser))
# and see how large that chunk was, remove that from buffer
self.buffer_net2ser = self.buffer_net2ser[n:]
except Exception as msg:
self.handle_serial_error(msg)
def handle_serial_error(self, error=None):
"""Serial port error"""
# terminate connection
self.close()
def handle_socket_read(self):
"""Read from socket"""
try:
# read a chunk from the serial port
data = self.socket.recv(1024)
if data:
# Process RFC 2217 stuff when enabled
if self.rfc2217:
data = b''.join(self.rfc2217.filter(data))
# add data to buffer
self.buffer_net2ser.extend(data)
else:
# empty read indicates disconnection
self.handle_disconnect()
except socket.error:
if self.log is not None:
self.log.exception("{}: error reading...".format(self.device))
self.handle_socket_error()
def handle_socket_write(self):
"""Write to socket"""
try:
# write a chunk
count = self.socket.send(bytes(self.buffer_ser2net))
# and remove the sent data from the buffer
self.buffer_ser2net = self.buffer_ser2net[count:]
except socket.error:
if self.log is not None:
self.log.exception("{}: error writing...".format(self.device))
self.handle_socket_error()
def handle_socket_error(self):
"""Socket connection fails"""
self.handle_disconnect()
def handle_connect(self):
"""Server socket gets a connection"""
# accept a connection in any case, close connection
# below if already busy
connection, addr = self.server_socket.accept()
if self.socket is None:
self.socket = connection
# More quickly detect bad clients who quit without closing the
# connection: After 1 second of idle, start sending TCP keep-alive
# packets every 1 second. If 3 consecutive keep-alive packets
# fail, assume the client is gone and close the connection.
self.socket.setsockopt(socket.SOL_SOCKET, socket.SO_KEEPALIVE, 1)
self.socket.setsockopt(socket.IPPROTO_TCP, socket.TCP_KEEPIDLE, 1)
self.socket.setsockopt(socket.IPPROTO_TCP, socket.TCP_KEEPINTVL, 1)
self.socket.setsockopt(socket.IPPROTO_TCP, socket.TCP_KEEPCNT, 3)
self.socket.setblocking(0)
self.socket.setsockopt(socket.IPPROTO_TCP, socket.TCP_NODELAY, 1)
if self.log is not None:
self.log.warning('{}: Connected by {}:{}'.format(self.device, addr[0], addr[1]))
self.serial.rts = True
self.serial.dtr = True
if self.log is not None:
self.rfc2217 = serial.rfc2217.PortManager(self.serial, self, logger=log.getChild(self.device))
else:
self.rfc2217 = serial.rfc2217.PortManager(self.serial, self)
else:
# reject connection if there is already one
connection.close()
if self.log is not None:
self.log.warning('{}: Rejecting connect from {}:{}'.format(self.device, addr[0], addr[1]))
def handle_server_error(self):
"""Socket server fails"""
self.close()
def handle_disconnect(self):
"""Socket gets disconnected"""
# signal disconnected terminal with control lines
try:
self.serial.rts = False
self.serial.dtr = False
finally:
# restore original port configuration in case it was changed
self.serial.apply_settings(self.serial_settings_backup)
# stop RFC 2217 state machine
self.rfc2217 = None
# clear send buffer
self.buffer_ser2net = bytearray()
# close network connection
if self.socket is not None:
self.socket.close()
self.socket = None
if self.log is not None:
self.log.warning('{}: Disconnected'.format(self.device))
def test():
service = ZeroconfService(name="TestService", port=3000)
service.publish()
input("Press the ENTER key to unpublish the service ")
service.unpublish()
if __name__ == '__main__': # noqa
import logging
import argparse
VERBOSTIY = [
logging.ERROR, # 0
logging.WARNING, # 1 (default)
logging.INFO, # 2
logging.DEBUG, # 3
]
parser = argparse.ArgumentParser(
usage="""\
%(prog)s [options]
Announce the existence of devices using zeroconf and provide
a TCP/IP <-> serial port gateway (implements RFC 2217).
If running as daemon, write to syslog. Otherwise write to stdout.
""",
epilog="""\
NOTE: no security measures are implemented. Anyone can remotely connect
to this service over the network.
Only one connection at once, per port, is supported. When the connection is
terminated, it waits for the next connect.
""")
group = parser.add_argument_group("serial port settings")
group.add_argument(
"--ports-regex",
help="specify a regex to search against the serial devices and their descriptions (default: %(default)s)",
default='/dev/ttyUSB[0-9]+',
metavar="REGEX")
group = parser.add_argument_group("network settings")
group.add_argument(
"--tcp-port",
dest="base_port",
help="specify lowest TCP port number (default: %(default)s)",
default=7000,
type=int,
metavar="PORT")
group = parser.add_argument_group("daemon")
group.add_argument(
"-d", "--daemon",
dest="daemonize",
action="store_true",
help="start as daemon",
default=False)
group.add_argument(
"--pidfile",
help="specify a name for the PID file",
default=None,
metavar="FILE")
group = parser.add_argument_group("diagnostics")
group.add_argument(
"-o", "--logfile",
help="write messages file instead of stdout",
default=None,
metavar="FILE")
group.add_argument(
"-q", "--quiet",
dest="verbosity",
action="store_const",
const=0,
help="suppress most diagnostic messages",
default=1)
group.add_argument(
"-v", "--verbose",
dest="verbosity",
action="count",
help="increase diagnostic messages")
args = parser.parse_args()
# set up logging
logging.basicConfig(level=VERBOSTIY[min(args.verbosity, len(VERBOSTIY) - 1)])
log = logging.getLogger('port_publisher')
# redirect output if specified
if args.logfile is not None:
class WriteFlushed:
def __init__(self, fileobj):
self.fileobj = fileobj
def write(self, s):
self.fileobj.write(s)
self.fileobj.flush()
def close(self):
self.fileobj.close()
sys.stdout = sys.stderr = WriteFlushed(open(args.logfile, 'a'))
# atexit.register(lambda: sys.stdout.close())
if args.daemonize:
# if running as daemon is requested, do the fork magic
# args.quiet = True
# do the UNIX double-fork magic, see Stevens' "Advanced
# Programming in the UNIX Environment" for details (ISBN 0201563177)
try:
pid = os.fork()
if pid > 0:
# exit first parent
sys.exit(0)
except OSError as e:
log.critical("fork #1 failed: {} ({})\n".format(e.errno, e.strerror))
sys.exit(1)
# decouple from parent environment
os.chdir("/") # don't prevent unmounting....
os.setsid()
os.umask(0)
# do second fork
try:
pid = os.fork()
if pid > 0:
# exit from second parent, save eventual PID before
if args.pidfile is not None:
open(args.pidfile, 'w').write("{}".format(pid))
sys.exit(0)
except OSError as e:
log.critical("fork #2 failed: {} ({})\n".format(e.errno, e.strerror))
sys.exit(1)
if args.logfile is None:
import syslog
syslog.openlog("serial port publisher")
# redirect output to syslog
class WriteToSysLog:
def __init__(self):
self.buffer = ''
def write(self, s):
self.buffer += s
if '\n' in self.buffer:
output, self.buffer = self.buffer.split('\n', 1)
syslog.syslog(output)
def flush(self):
syslog.syslog(self.buffer)
self.buffer = ''
def close(self):
self.flush()
sys.stdout = sys.stderr = WriteToSysLog()
# ensure the that the daemon runs a normal user, if run as root
# if os.getuid() == 0:
# name, passwd, uid, gid, desc, home, shell = pwd.getpwnam('someuser')
# os.setgid(gid) # set group first
# os.setuid(uid) # set user
# keep the published stuff in a dictionary
published = {}
# get a nice hostname
hostname = socket.gethostname()
def unpublish(forwarder):
"""when forwarders die, we need to unregister them"""
try:
del published[forwarder.device]
except KeyError:
pass
else:
log.info("unpublish: {}".format(forwarder))
alive = True
next_check = 0
# main loop
while alive:
try:
# if it is time, check for serial port devices
now = time.time()
if now > next_check:
next_check = now + 5
connected = [d for d, p, i in serial.tools.list_ports.grep(args.ports_regex)]
# Handle devices that are published, but no longer connected
for device in set(published).difference(connected):
log.info("unpublish: {}".format(published[device]))
unpublish(published[device])
# Handle devices that are connected but not yet published
for device in sorted(set(connected).difference(published)):
# Find the first available port, starting from specified number
port = args.base_port
ports_in_use = [f.network_port for f in published.values()]
while port in ports_in_use:
port += 1
published[device] = Forwarder(
device,
"{} on {}".format(device, hostname),
port,
on_close=unpublish,
log=log)
log.warning("publish: {}".format(published[device]))
published[device].open()
# select_start = time.time()
read_map = {}
write_map = {}
error_map = {}
for publisher in published.values():
publisher.update_select_maps(read_map, write_map, error_map)
readers, writers, errors = select.select(
read_map.keys(),
write_map.keys(),
error_map.keys(),
5)
# select_end = time.time()
# print "select used %.3f s" % (select_end - select_start)
for reader in readers:
read_map[reader]()
for writer in writers:
write_map[writer]()
for error in errors:
error_map[error]()
# print "operation used %.3f s" % (time.time() - select_end)
except KeyboardInterrupt:
alive = False
sys.stdout.write('\n')
except SystemExit:
raise
except:
#~ raise
traceback.print_exc()